In order to measure particles, such as soot particles, in the exhaust gas of internal combustion engines, a particle sensor having a device for the detection of soot particles may be mounted in the exhaust pipe.
A sensor is discussed in German patent document no. DE 101 33 384 A1 which is made up of two base (substrate) elements, the base elements having interdigital electrodes and an integrated heater, and being laminated to each other. The interdigital electrodes are used for measuring soot particles, the measurement being based on a resistive measuring principle: An accumulation of particles on the electrode structure leads to a conductivity change or impedance change of the area between the combs of the electrode. From the change, the accumulation, or rather, the accumulation rate of the particles may be derived. After a certain accumulation quantity, the sensor has to be regenerated, that is, the sensor has to be freed of accumulated particles. To do this, the integrated heater heats the sensor encumbered with soot, so that the accumulated soot is completely burned off. Then the sensor is again in the original state, and a renewed accumulation and measurement of particles are thereby made possible.
One advantage of this procedure comes about because, during the combustion, no new accumulation of particles is possible. Even after the regeneration, soot cannot immediately be accumulated again, for, because of thermal inertia, the sensor requires a certain time for the thermalization of the sensor element by the exhaust gas. Since, during the regeneration phase and the subsequent cooling phase of the sensor, no soot is able to be accumulated, during these phases the sensor is insensitive with respect to a possibly present soot concentration.